Grudges against a religious group were expressed in social media posts believed to have been written by the man accused of murdering former Prime Minister Abe Shinzo.

Investigators have learned that the suspect, Yamagami Tetsuya, had developed animosity toward the Family Federation of World Peace and Unification, formerly known as the Unification Church, to which his mother had donated money,. The 41-year-old was arrested at the scene of the fatal shooting of Abe in Nara City on July 8.

Just before the shooting, Yamagami is believed to have posted a letter saying Abe was not his primary adversary, even though the former prime minister was one of the most influential sympathizers of the group.

Yamagami is also believed to have repeatedly expressed his resentment against the group on Twitter in recent years. Such posts include one saying that the only thing he hates is the Unification Church, so he doesn't care what happens to Abe's administration. Another one says, "My family fell apart when I was 14."

The head of the Japan branch of the religious group told reporters that Abe was not a member or advisor. He also said Abe presented a message at an event hosted by an affiliated organization.

The group says that it has not been able to find out the timing and amount of the suspect's mother's donations.

It has said it returned a total of 50 million yen, or about 400,000 dollars, to the suspect's mother over a 10 years through 2014.

Investigators are trying learn more about how the suspect's grudges against the group may have led him to attack the former prime minister.